Word Study
septi-
CIDE DICTIONARY
septi-, [L. septem seven.].
A combining form meaning seven; as, septifolious, seven-leaved; septi-lateral, seven-sided. [1913 Webster]
OXFORD DICTIONARY
septi-, comb. form (also sept- before a vowel) seven.
Etymology
L f. septem seven
For further exploring for "septi-" in Webster Dictionary Online