The American Heritage® Dictionary of the English Language: Fourth Edition. 2000.
Appendix I
Indo-European Roots
ENTRY:
segh-
DEFINITION:
To hold. Oldest form *seh-, becoming *segh- in centum languages. Derivatives include hectic, eunuch, scheme, and scholar. 1. Suffixed form *segh-es-.Siegfried, from Old High German sigu,sigo, victory, from Germanic *sigiz-, victory (< “a holding or conquest in battle”). 2.hectic; cachexia, cathexis, entelechy, eunuch, Ophiuchus, from Greek ekhein, to hold, possess, be in a certain condition, and hexis, habit, condition. 3. Possible suffixed (abstract noun) form *segh-wr, toughness, steadfastness, with derivative *segh-wr-o-, tough, stern. severe; asseverate, persevere, from Latin sevrus, stern; b.sthenia; asthenia, calisthenics, hypersthene, hyposthenia, thrombosthenin, from Greek sthenos, physical strength, from a possible related abstract noun form *sgh-wen-es- (with zero-grade of the root). 4. O-grade form *sogh-.epoch, from Greek epokh, “a holding back,” pause, cessation, position in time (epi-, on, at; see epi). 5. Zero-grade form *sgh-.a.scheme, from Greek skhma, “a holding,” form, figure; b.scholar, scholastic, scholium, school1, from Greek skhol, “a holding back,” stop, rest, leisure, employment of leisure in disputation, school. 6. Reduplicated form *si-sgh-.ischemia, from Greek iskhein, to keep back. (Pokorny seh- 888.)
h-, becoming *segh- in centum languages. 
r, toughness, steadfastness, with derivative *segh-w
