means Feeling annoyed, bothered, or impatient — or, of skin and tissue, inflamed and sore.

from From Latin irritare, "to excite, provoke, enrage," which gives us the past participle irritatus. English borrowed it in the 1500s, and from the start it carried both senses we still use: the mind that's been provoked and the flesh that's been rubbed raw. The two meanings are really one idea — something has been stirred up that would rather be left alone.