An Etymological Dictionary of Astronomy and Astrophysics

1a) The act or state of touching or being in immediate proximity, as in a → contact binary.

1b) One of the instances when the apparent position of the edges of the Sun and the Moon cross one another during an eclipse. They are designated as the → first contact, → second contact, → third contact, and → fourth contact.
See also → contact binary, → last contact.

2a) (v. intr.) To be in or come into contact.

2b) (v.tr.) To bring or put in contact.

Etymology (EN): From L. contactus “a touching,” p.p. of contingere “to touch,” from → com- “together” + tangere “to touch.”

Etymology (PE): Parmâs “contact, touching,” stem of parmâsidan “to touch, feel,” from *pari-mars-, from Indo-Iranian *pari- “around” (O.Pers. pariy “around, about,” Av. pairi “around, over,” Skt. pari) + *mars- “to touch; to wipe, rub,” Mid.Pers. marz “contact, touching,” marzitan “to touch,” Mod.Pers. mâlidan “to rub,” Av. marəz- “to rub, wipe,” marəza- “border, district,” Skt. mrś- “to touch,” mrśáti; L. mulceo “to caress,” margo “edge” (Fr. marge “margin”); P.Gmc. *marko;
Ger. Mark; E. mark, margin.