You can see it very clearly in ingrate, which was originally an adjective in the 14th century, and originally meant “unfriendly, unpleasant.” The connection between pleasant feelings and thankfulness for the pleasantness is a recurring one, which I think is telling. By around 1670 ingrate had come to mean the person with that quality of being unpleasant and simultaneously failing to be thankful for gifts.
You can see the same Latin root that gave grate in congratulate, which essentially means showing pleasure with someone. Gratify comes from the idea of bestowing pleasure upon someone.
Another suite of words that come from the idea of giving thanks includes
gratis - meaning something done for thanks only, rather than payment
gratuitous - which originally meant the same as gratis, but by about 1690 (some 40 years later), meant “uncalled for, done without good reason.”
gratuity - the idea being that it’s money you didn’t have to give in payment, but rather bestowed in thanks
And speaking of thanks, that’s from all the way back in Old English, and seems to be related to think. Again, isn’t it suggestive that thinking of the things and relationships we have is so closely related to giving thanks for them? That’s why it’s important to count our blessings, even when there’s also so much to be concerned about.
[Picture: Mexican Fruits, wood engraving by Leon Underwood, 1927 (Image from The New Woodcut, by Malcolm C. Salaman, 1930).]