Where does “senescere” come from?

senescere (Latin) comes from Latin senere, from Latin senex, from Proto-Indo-European sénos — old.

senescere (Latin): present active infinitive of senēscō; to grow old

Definitions

Step	Language	Word	Meaning
1	Latin	senere	to be old
2	Latin	senex	old, aged, elderly; old person, old man, old...
3	Proto-Indo-European	sénos	old

senescere — Etymology, Origin & Word History | Etymology Explorer