sobriety n.

mid-14c., sobre, "moderate in desires or actions, habitually temperate, restrained," especially "abstaining from strong drink," also "calm, quiet, not overcome by emotion," from Old French sobre "decent; sober" (12c.), from Latin sobrius "not drunk, temperate, moderate, sensible," from a variant of se- "without" (see se-) + ebrius "drunk," which is of unknown origin.

The meaning "free from the influence of intoxicating liquors; not drunk at the moment" is from late 14c.; also "appropriately solemn, serious, not giddy." As "plain or simple in color" by 1590s. Jocular sobersides "sedate, serious-minded person" is recorded from 1705.

early 14c., sobrenes, "state or character of being sober, moderation in desires or actions," from sober (adj.) + -ness. Also "gravity, seriousness" (late 14c.).