What is the X in X-mas?
1680s, from Latin inguinalis "of the groin," from inguen (genitive inguinis) "groin," from PIE *engw- "groin, internal organ" (cf. Greek aden "gland").
inguinal in·gui·nal (ĭng'gwə-nəl)
Of or located in the groin.
Relating to the left or right inguinal region of the abdomen.