mid-13c., "to practice habitually," from Anglo-French meintenir (Old French maintenir, 12c.) "keep (a wife), sustain; persevere in, practice continually," from Latin manu tenere "hold in the hand," from manu, ablative of manus "hand" (see manual) + tenere "to hold" (see tenet). Meaning "to carry on, keep up" is from mid-14c.; that of "to keep oneself, to support" is from late 14c. Sense of "to defend in speech" is from mid-14c. Related: Maintained; maintaining; maintains.
To stay under control; to keep one's composure: While he gives this silly speech, I need to maintain