The Proto-Indo-European word *h₂emros
Word *h₂emros
Meaning bitter, sour
See also Proto-Indo-European: *h₂em- ‘raw, bitter’
Synonyms *h₃em-, *kwat-, *suhₓros

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

Other words that might be of interest
*sweh₂d-u- ‘sweet’, *(s)terh₁- ‘stiff’, *st(h₂)eug- ‘stiff’