Discreet means careful not to draw attention or let anything slip. A discreet cough to stop a colleague talking, a discreet word with the manager instead of a scene at the till, a friend who knows everything about you and repeats none of it.
It works for things as much as for people: a discreet grey suit, a discreet sign by the door, a discreet amount of perfume — quiet, and not one of them noticeable. Now the trap, and it is the big one. Discrete, with the e's split by the t, means separate and countable: five discrete steps, discrete data. The noun for the discreet kind is discretion, which holds both threads — keeping quiet, and having the judgement to decide for yourself: I'll leave it to your discretion. The opposite is indiscreet, the person who tells you what everyone else said about you.
1adjectivediscreetCareful to say and show nothing that ought to stay private.
“The doctor was discreet about who else had been in that week.”
synonyms: tactful, circumspect
2adjectiveunobtrusiveNot noticeable; done or worn without drawing the eye.
“There was a discreet sign by the door and nothing else.”
synonyms: unobtrusive, understated
Also accepted in games: tactful
Discreet came through Old French discret from Latin discrētus, the past participle of discernere, 'to separate, to tell apart' — the same idea English keeps in discern. Someone discreet was, first of all, someone who could tell one thing from another: a person of judgement. English then borrowed that Latin word a second time and let the new copy keep the literal sense, as discrete, 'separate'. One Latin word, two English spellings, and centuries of people mixing them up.
Proto-Indo-European
*krey-
Latin
discrētus
Old French
discret
Middle English
discrete
English, today
discreet
From Middle English discrete, from Old French discret, from Latin discrētus, from past participle of discernere. a doublet of discrete.
Etymology from Wiktionary, CC BY-SA