contamination (n.)

early 15c., contaminacioun, "infection," from Medieval Latin contaminationem (nominative contaminatio) "a polluting, contamination, defilement," noun of action from past-participle stem of Latin contaminare "to defile, to corrupt, to deteriorate by mingling," originally "to bring into contact," from contamen "contact; pollution," from assimilated form of com "with, together" (see con-) + base of tangere "to touch" (from PIE root *tag- "to touch, handle"). Figurative sense is from c. 1620; specifically of radioactivity from 1913.