tamper (n.)

"one who or that which tamps," 1864, agent noun from tamp (v.).

tamper (v.)

"meddle, interfere," 1560s, figurative use of tamper "to work in clay, etc., so as to mix it thoroughly," probably originally a variant of temper (v.), which is how it often was spelled at first. Perhaps it is a dialectal workmen's pronunciation. Related: Tampered; tampering.