"small vessel used to contain liquids generally; drinking vessel," Old English cuppe, Old Northumbrian copp, from Late Latin cuppa "cup" (source of Italian coppa, Spanish copa, Old French coupe "cup"), from Latin cupa "tub, cask, tun, barrel," which is thought to be cognate with Sanskrit kupah "hollow, pit, cave," Greek kype "gap, hole; a kind of ship," Old Church Slavonic kupu, Lithuanian kaupas "heap," Old Norse hufr "ship's hull," Old English hyf "beehive." De Vaan writes that all probably are from "a non-IE loanword *kup- which was borrowed by and from many languages."
The Late Latin word was borrowed throughout Germanic: Old Frisian kopp "cup, head," Middle Low German kopp "cup," Middle Dutch coppe, Dutch kopje "cup, head." German cognate Kopf now means exclusively "head" (compare French tête, from Latin testa "potsherd").
Used of any thing with the shape of a cup by c. 1400; sense of "quantity contained in a cup" is from late 14c. Meaning "part of a bra that holds a breast" is from 1938. Sense of "cup-shaped metal vessel offered as a prize in sport or games" is from 1640s. Sense of "suffering to be endured" (late 14c.) is a biblical image (Matthew xx.22, xxvi.39) on the notion of "something to be partaken of."
To be in one's cups "intoxicated" is from 1610s (Middle English had cup-shoten "drunk, drunken," mid-14c.). [One's] cup of tea "what interests one" is by 1932, earlier used of persons (1908), the sense being "what is invigorating." Cup-bearer "attendant at a feast who conveys wine or other liquor to guests" is from early 15c.