The Proto-Indo-European word *(s)terh₁-
Word *(s)terh₁-
Meaning stiff
Synonyms *st(h₂)eug-

Comments
Mallory J.P. and Adams D. (2006)

Other words that might be of interest
*h₃em- ‘bitter’, *kwat- ‘sour’, *sweh₂d-u- ‘sweet’, *h₂em- ‘raw, bitter’, *suhₓros ‘sour, acid’, *h₂emros ‘bitter, sour’