contineo

Contineo, continere, continui, contentum, second conjugation. It is con plus teneo with the vowel weakened, and the sense is "hold together": to contain, to enclose, to hold back. Active it takes a plain accusative; passive it is the ordinary Latin for a thing consisting in or bounded by something, with the bare ablative and no preposition - muro continetur, libro continetur.

The participle contentus is the same word doing quiet work: a contented man is one held within his own limits, which is a more austere idea than the English suggests. Continens gives both the continent as a landmass, terra continens, "unbroken land", and continence, the self-restrained sense. The reflexive se continere is the standard way to say "keep one's temper".