Definition - Words that derive from the same etymological roots — e.g. doublets.
Note: Words that exhibit this quality are described as being paronymous.

Example -

(1) The words hospital, hostel, and hotel are triplets that derive from the Medieval Latin hospitale, inn.
(2) The words aperture and overture are doublets that derive from the Latin aperire, to open.

Etymology -
The word derives from the Greek paronumos, derivative (from para, beside + onuma, name).

Oxford English Dictionary -
The first citation for paronymous is from 1661:
"Paronymous (Gr.), pertaining to words or terms that have denomination from the same thing, but differ in case or termination."
(Blount, Glossographia (ed. 2))

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