contiguity (n.)

1620s, "action, state, or condition of touching," from Latin contactus "a touching" (especially "a touching of something unclean, contamination"), from past participle of contingere "to touch, seize," from assimilated form of com "with, together" (see con-) + tangere "to touch," from PIE root *tag- "to touch, handle."

The figurative sense of "a connection, communication" is attested from 1818. The meaning "a person who can be called upon for assistance" is attested by 1931. As a call to the person about to spin an aircraft propeller to signal that the ignition is switched on, contact was in use by 1913.

To make contact (1860) originally was in reference to electrical circuits. Contact lens " thin artificial lens placed directly on the surface of the eye to correct visual defects" is first recorded 1888, in a translation of an article published in Zurich in 1887 by A. Eugen Fick; contacts for "contact lenses" is from 1957. Contact sport, for one involving bodily contact, is attested from 1922.