The words onion and union differ in only one letter, and there’s a reason they are so similar. The word onion is derived from union, you can see why if you think about how those numerous scales are united in an onion bulb.
Unlike onion and union, sometimes the literal meaning of a food name isn't so obvious, especially for names from other languages. Burrito, for example, is literally a "little donkey," from Spanish burro (donkey) + ito(the diminutive affix). Let's look at more words with unusual origins. Sometimes they are named after a shape, at other times for their colors, and often whimsically for something else.
Baguette - stick, from French.
Cabbage - head, via French from Latin caput (head).
Calzone - trouser leg, from Italian.
Candy - piece, from Sanskrit khand (piece).
Cannoli - tube, from Italian, plural of cannolo.
Cappuccino - Capuchin monk, from Italian. The color of a cappuccino resembles that of a friar's habit.
Chimichanga - trinket, from Spanish.
Date - finger, from Greek daktulos (finger), from its shape.
Enchilada - seasoned with chili, from Spanish enchilar (to season with chili).
Gnocchi - knot in wood, from Italian nocchio. (Also the origin of Pinocchio).
Halibut - holy flatfish, from Middle English Hali (holy) and butte(flatfish), because it was eaten on holy days.
Marinara - in sailor's style, from Italian.
Meat - food. Earlier meat was any food, not necessarily animal flesh. That's why sweetmeat is a sweet delicacy, not made of animals (but sweetbread is).
Taco - plug or wad, from Spanish.
Tamarind - Indian date, from Arabic tamr (date) and hindi (Indian).
Tapas - covers, lids, from Spanish tapa (cover or lid). Because in many parts of Spain these snacks are offered with a drink in bars and cafes, often the plate (or the snack itself) is put on of the drink.
Tutti-frutti - all fruit, from Italian tutta (all) and frutta (fruit).
Vermicelli - little worms, plural of Italian vermicello, diminutive of verme (worm).
Walnut - foreign nut, from Old English from wealhhnutu from wealh(Welsh, foreigner) and hnutu (nut). It was formerly also known as walsh-nut.