de·mean 1 (dĭ-mēn') tr.v.
de·meaned, de·mean·ing, de·means To conduct or behave (oneself) in a particular manner: demeaned themselves well in class.
[Middle English demeinen, to govern, from Old French demener : de-, de- + mener, to conduct (from Latin mināre, to drive (animals), from minārī, to threaten, from minae, threats; see men-2 in Indo-European roots).]
"lower in dignity," 1601, perhaps from de- "down" + mean (adj.) and modeled on debase. Indistinguishable in some uses from obsolete demean (see demeanor) which influenced it and may be its true source.