I am thankful to my daughter for pointing out dates was the staple food of Indus valley and Mr. Raveen Nathan for his facebook post on F.C.Southworth’s paper.
Dates is one of the most nutritious fruits and is a staple food across Middle East and South Asia. Dates was harvested pre historically in the regions of Africa, Mesopotamia and Indus Valley.
Excavations in Mehrgarh have show evidence of earliest settled agriculture in South Asia. There is evidence of cultivation of wheat, barley and dates pre 5000 BCE. . Also in Mature Harappa phase around 2500 BCE, we have evidence of Dates cultivation in Harappa and Mohenjo-Daro .
Dates is highly nutritious fruit and has large shelf life.
“All parts of the date palm yield products of economic value. Its trunk furnishes timber; the midribs of the leaves supply material for crates and furniture; the leaflets, for basketry; the leaf bases, for fuel; the fruit stalks, for rope and fuel; the fiber, for cordage and packing material; and the seeds are sometimes ground and used as stock feed. Syrup, alcohol, vinegar, and a strong liquor are derived from the fruit. The sap is also used as a beverage, either fresh or fermented, but, because the method of extraction seriously injures the palm, only those trees that produce little fruit are used for sap. When a palm is cut down, the tender terminal bud is eaten as a salad.” 
Even today Pakistan’s Sindh area is one of the biggest producers of the dates fruit. In fact, the pre historic cultivation sites are still major producers of dates.
We have even reference in Mespotamian records that dates were imported from Indus Valley.
Inscription of Sargon of Akkad mentions ships from Meluhha (Indus Valley) came to Akkad.
gis-gisimmar Me luh ha -> Date palm of Meluhha 
Also from Third dynasty period 2029-2006 BCE or Larsa period (1822-1763 BCE) we have record of Date palm from Meluhha. 
” Other items of commerce associated with Meluhha including date-palms, A.AB.BA wood identified as mangrove, carnelians, and copper, as we have seen, are found in eastern Baluchistan
and no doubt would have been traded more directly at the coastal ports by the merchants of this region.” 
From the above records we can clearly say Dates was one of the important tree of the Indus valley.
Now let us jump to Etymology of the dates in Tamil and other Dravidian languages.
As a Tamil, the first thing that we would recall when we hear ‘dates’ is probably Lion dates promos or probably Karagatakaran comedy when we hear the Tamil word ‘Perchampalam’.
Let us first look at etymological history of the Tamil word for the name of the fruit,
Perchampalam -> Per + īccu +Palam (Big Ichu fruit)
īccu is corruption of the word īñcu, which itself is a corruption of the word īntu
This can be verified from the the Tamil Lexicon entries
பேரீச்சு pēr-īccu – , n. See பேரீந்து
பேரீஞ்சு pēr-īñcu – See பேரீந்து
பேரீந்து pēr-īntu , Date-palm, Phoenix dactylifera;
Let us now look at the root word ஈந்து īntu
1. Datepalm, m. tr., Phoenix doctylifera; பேரீச்சமரம்.
2. Dwarf wild datepalm, m. sh., Phoenix farinifera; சிற்றீந்து
Usage of ஈந்து īntu is very common in Sangam literature/ Old Tamil
ஈத்து இலை வேய்ந்த 88
களர் வளர் ஈந்தின் காழ் கண்டன்ன 130
ஈத்திலை குப்பை ஏறி உமணர்
உதிர்ந்த பைங்குலை ஈந்தின்
செங்காய் உதிர்த்த பைங்குலை ஈந்தின்
கற்றை ஈந்தின் முற்றுக் குலை அன்ன
ஒலி வல் ஈந்தின் உலவைஅம் காட்டு
கருங் களி ஈந்தின் வெண் புறக் களரி
It is pretty clear from Dravidian Etymological dictionary, the word īntu and its variants are spread across all Dravidian languages to denote varieties of date palm (entry 2617).
Prof. Franklin Southworth has reconstructed the Early Proto Dravdian version of the word for dates as Kīntu or cīntu and later Proto Dravidian version as cīntu (pronounced as sindu/cindu).
Per Southworth, Dravidian language chain has the earliest word for dates, pre dating Munda and Indo Aryan Languages. 
He quotes Nurse’s proto Bantu reconstruction of term for date as ‘mu Kindu’ being similar to proto Dravidian version. Nurse’s paper reconstructs the proto Bantu version from present day Northern and Southern dialects of Swahili (mkindu – dates) 
Southworth proposes that either dates was named after Indus (river/land) or vice versa.
We see a similar trend in Indo – Aryan languages as well.
Per Dravidian Etymological dictionary the below Indo -Aryan words for dates are possible loan words from Dravidian.
Indo – Aryan:
Sanskrit: hintāla- the marshy date tree, Phoenix or Elate paludosa
Prakrit: sindī- date-palm, khajūrī; Savara sindī-n a variety of date or toddy tree.
This was cross verified with A comparative dictionary of Indo-Aryan languages and the following entry suggests in fact sindi is a loan word for dates in Indo -Aryan languages
13410 *sindī ʻ date — palm ʼ;pk. siṁdī, siṁdōlī — date — palm ʼ; M. śĩd, śĩdī, śĩdhī f. ʻ wild date — palm ʼ.
If Southworth reconstruction is true that it means, Proto Dravidian word cīntu is the root word for Indus, India, Hindu, Hindi.
Considering the current politics in India, it would be an irony if the etymology of Hindi and Hindu points to a Dravidian root word.
1 Allchin, B. and F. R. Allchin (1982) The Rise of Civilization in India and Pakistan,
Cambridge: Cambridge University Press; pg. 108
2 Allchin, B. and F. R. Allchin (1982) The Rise of Civilization in India and Pakistan,
Cambridge: Cambridge University Press; pg. 191
Marshall, Sir John (1931) Mohenjo-Daro and the Indus Civilization, Vols. 1–3. London:
Arthur Probstain. pg. 27,587
Vats, M. S. (1940) Excavations at Harappa, Delhi: Government of India. Pg. 467
4 Leemans. W.F. 1960. Foreign Trade in the Old Babylonian Period. Leiden. pg.160
5 John Hansman (1973), A “Periplus” of Magan and Meluḫḫa, Bulletin of the School of Oriental and African Studies, University of London, Vol. 36,No. 3 , pg. 557
6 ibid. pg. 562
7 Southworth, F.C., The reconstruction of prehistoric South Asian language contact, The uses of linguistics (ed. E.Bendix), New York Academy of Sciences, Pg. 228
8 Southworth, F.C. (1988) , Ancient economic plants of South Asia: linguistic archaelogy and earlu agriculture, Languages and cultures: studies in honor of Edgar C. Polome, pg. 657
9 Nurse, Derek (1983), A linguistic reconsideration of Swahili origins. Azania XVIII:127-50
10 Southworth, F.C., The reconstruction of prehistoric South Asian language contact, The uses of linguistics (ed. E.Bendix), New York Academy of Sciences, Pg. 228
Dravidian Etymological Dictionary
University of Madras – Tamil Lexicon
A comparative dictionary of Indo-Aryan Languages
Ratnagar, S. (1981) Encounters, the Westerly Trade of the Harappa Civilization, Delhi:
Oxford University Press. Pg 8
Southworth, F.C., LINGUISTIC ARCHAEOLOGY OF SOUTH ASIA
Learn Sangam Tamil