An Etymological Dictionary of Astronomy and Astrophysics

1. To strike together with forceful impact, such as two astronomical objects.
   
2. Of two or more atomic particles, to approach closely resulting in an abrupt change of momentum or exchange of energy.

Etymology (EN): From L. collidere “to strike together,” from col- variant of → com- “together” + laedere “to strike,” of unknown origin.

Etymology (PE): Ham- “together, with,” → com-

• kubidan, kuftan “to beat, strike, pound,” kus “drum,” Mid.Pers. kôftan and kôstan “to beat, strike.”