"duplicated, found in pairs," early 15c., from Latin geminatus "twinned, equal," past participle of geminare "to double, repeat," related to geminus "twin, born together; paired, double," perhaps from PIE *yem- "to pair." As a verb, from 1630s. Related: Geminated; geminating; geminative.
The consonants are geminated in these words
the `n' in `thinness' is a geminate
gelt
gem
gematria
*gembh-
gemeinschaft
geminate
gemination
Gemini
gemmologist
gemstone
-gen
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