Tester
Likely a surname from an old French personal name, though it was also influenced by words for a test vessel or headpiece.
The #7,663 most common surname in the United States (2010 Census) — about 1 in every 71,238 Americans shares it.
Etymology
Most evidence points to an origin in the Old French baptismal name Testard, recorded very early and probably built on test- / têst- forms connected with 'head' or 'skull.' Some 19th-century writers also linked the surname to Old French teste, 'a testing-pot' or refining vessel, from Latin testa, but that is a weaker surname explanation. The name may also have been reinforced by related French forms such as Testaert or Teste.
History
The surname appears in medieval English records and was treated by older surname scholars as a French import. Lower and Bardsley both connect it mainly with the personal name Testard, while Harrison notes a possible occupational sense from the 'assay pot' word. In England it remained uncommon but persistent, with variant spellings such as Testar and Testard.
Origin
Regions
Variant spellings
Fun fact
A different English word tester can mean a canopy or a bed-hanging, but that is unrelated to the surname.
From the historical record
“frequent. TESTER I (A.-Fr.-Lat.) 1 Assaykr [f. (with TESTARJ the agent, suff. -er) M.E. O.Fr. teste, a testing-pot, refining-pot; Lat. testa, apotj » for Testardi q.v, Tetbury”
— Surnames of the United Kingdom: a concise etymological dictionary (2 vols in 1)