We call those common gifts of God to man "common grace" because they are

(1) Common gifts among all humans,
and
(2) Freely given, unmerited gifts from God.

(1) corresponds to the "common" part of "common grace," and (2) corresponds to the "grace" part. Neither is an abuse of language. If somebody can't get their head around how there can be various kinds and degrees of grace, while all of these kinds or degrees are "grace" nonetheless, then they're not trying too hard.

John


"He that hath light thoughts of sin, never had great thoughts of God." ...John Owen