Why is the ninth month called September?
c.1400, perhaps existing in Old English as a word meaning "pothole," perhaps ultimately from Proto-Germanic *dumpilaz, which has yielded words in other languages meaning "small pit, little pool" (e.g. German Tümpel "pool," Middle Low German dümpelen, Dutch dompelen "to plunge"). Related: Dimples.
1570s (implied in dimpled), from dimple (n.).
dimple dim·ple (dĭm'pəl)
A small natural indentation in the chin, cheek, or sacral region, probably due to some developmental fault in the subcutaneous connective tissue or in underlying bone.
A depression of similar appearance resulting from trauma or the contraction of scar tissue.