The surrounding truth a thing is understood within. Nothing in this Grammar means alone; context is the room a meaning stands in.
Latin contextus (a joining, connection), from contexere (to weave together), from com- (together) + texere (to weave); the surrounding weave a thing is understood within, without which no meaning stands alone.
Latin's weaving sense is literal here: a meaning is a single thread, and context is everything woven around it that keeps it from unraveling into something else. Pull a word out of its weave and it can say almost anything.