means Belonging to the present time or recent past, as opposed to the ancient or the old-fashioned.

from From the Late Latin 'modernus,' meaning 'of the present,' built on the Latin adverb 'modo'—'just now, recently.' So at its root, 'modern' literally means 'now-ish,' which is exactly why it keeps slipping: every era inherits the word, points it at itself, and then watches it slide into the past it was supposed to escape. It entered English in the 1500s by way of Old French, and has been outrunning its own meaning ever since.