An Etymological Dictionary of Astronomy and Astrophysics

1. (v.tr.) To join or connect together; to bring together or into relationship in any of various intangible ways (as in memory or imagination). → dissociate.
   

2. (v.intr.) To come or be together as partners, friends, or join with other parts.
   

3. A person joined with another or others in business or at work; something that usually accompanies another thing.

Etymology (EN): M.E. associat “associated,” from L. associatus, p.p. of associare “to unite,” from ad- + sociare “to join,” from socius “ally, companion” (“follower”); PIE base *sek^w- “to follow.”

Etymology (PE): Âhazidan, from â- prefix + hazidan “to associate, accompany, follow,” from Av. hac-, hax- “to associate, follow, accompany” (hacenay- “getting together, association,” haxay-, hašy-, haš- “friend”), hacaiti “follows;”
hacā “from, out of;” O.Pers. hacā “from” (Mid.Pers. hâz- “to lead, guide,”
hac “from;” Mod.Pers. az “from”);
PIE base *sek^w- “to follow;”
cf. Skt. sac- “to be associated or united with,” sácate “accompanies, follows,” sácā “with;” Gk. hepesthai “to follow;” L. sequi “to follow.”
Âhazgâr, from âhaz- present stem of âhazidan + agent noun suffix -gâr, → -or, as in âmuzgâr, parhizgâr, sâzgâr, âmizgâr, sepuzgâr.