countertop (n.)

mid-14c., "table where a money lender does business," from Old French contouer, comptoir "counting room; table or bench of a merchant or bank" (14c.), from Medieval Latin computatorium "place of accounts," from Latin computatus, past participle of computare "to count, sum up, reckon together" (see compute).

Generalized 19c. from banks to shops, then extended to display cases for goods. In reference to a similar construction in a home kitchen by 1875. Over-the-counter in reference to goods sold and money paid is by 1875; phrase under the counter in reference to illegal or clandestine transactions is by 1926.

"highest point," Old English top "summit, crest, tuft," from Proto-Germanic *toppa- (source also of Old Norse toppr "tuft of hair," Old Frisian top "tuft," Old Dutch topp, Dutch top, Old High German zopf "end, tip, tuft of hair," German Zopf "tuft of hair"); no certain connections outside Germanic except a few Romanic words probably borrowed from Germanic.

Few Indo-European languages have a word so generic, which can be used of the upper part or surface of just about anything. More typical is German, which has Spitze for sharp peaks (mountains), oberfläche for the upper surface of flat things (such as a table). The meaning "highest position" is from 1620s; the meaning "best part" is from 1660s. The sense of "dominant sexual partner" is by 1961.

To go over the top is World War I slang for "start an attack," in reference to the top of the trenches; as "beyond reasonable limits, too far" it is recorded from 1968. Top of the world as "position of greatest eminence" is from 1670s. Top-of-the-line (adj.) is by 1950.