Why was clemency trending last week?
"one who tests," 1660s, agent noun from test (v.).
"canopy over a bed," late 14c., from Medieval Latin testerium, from testera "head stall," from Late Latin testa (capitis) "skull," from Latin, literally "earthenware, pot." The "head" sense (originally merely humorous) is the source of tester in obsolete senses of "piece of armor for the head" (late 14c.) and "coin of Henry VIII" (1546), the first English coin to bear a true portrait. For sense development, cf. Old English cuppe "cup" from source of German kopf "head."