irritation (n.) Look up irritation at Dictionary.com
early 15c., in physiology, in reference to sores and morbid swelling, from Middle French irritation or directly from Latin irritationem (nominative irritatio) "incitement, stimulus; irritation, wrath, anger," noun of action from past participle stem of irritare "to excite, provoke" (see irritate). Meaning "impatient or angry excitement" is from 1703.