Present participle of 'chin,' meaning to do a chin-up exercise or to move upward by grasping and lifting with one's chin or hands.
From the noun 'chin' plus the gerund '-ing.' Originally a gymnastics term that became standard fitness vocabulary in the 20th century.
Chinning bars were invented in the late 1800s for physical education, and doing chins (chin-ups) became a test of upper-body strength—but interestingly, women weren't expected to do them for decades even though they're just as capable! The gender bias in fitness is slowly changing.
Complete word intelligence in one call. Free tier — 50 lookups/day.