tester n.1

as a type of women's tall dressed hair or wig, 1756, from French tête "head," Old French teste, from Latin testa, literally "piece of earthenware, tile, potsherd; earthen pot, pitcher, jug; shell of shellfish," related to Latin testudo "tortoise" and texere "to weave" (compare Lithuanian tištas "vessel made of willow twigs"), from PIE root *teks- "to weave," also "to fabricate."

The "head" sense arose in Vulgar Latin, perhaps as a humorous use of the "jug, pot" meaning, or via Late Latin use of testa as "skull," from testa (capitis) "shell (of the head)." Compare German Kopf "head" from the root of English cup (n.).

1748, "to examine the correctness of," from test (n.), on the notion of "put to the proof." Earlier "assay gold or silver" in a test (c. 1600). Meaning "to administer a test" is from 1939; sense of "undergo a test" is from 1934. Related: Tested; testing.

1922, American English colloquial, of uncertain origin, perhaps related to slang tizzy "sixpence piece" (1804), a corruption of tester, a name for the coin (see tester (n.2)).