"Companionable" is the adjective form of "companion," which ultimately derives from a combination of the Latin prefix com-, meaning "with" or "together," and the noun panis, meaning "bread, loaf, or food." "Companionable" first appeared in print in English in the 16th century (companion has been in use since the 14th).

Is companion a noun?

COMPANION (noun) definition and synonyms | Macmillan Dictionary.

Is companion an adverb?

In a companionable manner; agreeably, sociably.