Proto-IE: *pep-
Meaning: weak
Old Greek: pépōn, n. -on, gen. -onos 'ripe; mild', pepái̯nō 'to ripen; to soften, assuage', pepái̯nomai̯ '(of tumors) to soften and suppurate; to grow warm' (formally, these forms are hardly separated from *pekʷ- ' to cook')
Russ. meaning: мягкий, слабый
References: Fraenkel 240 (different in Pok.)