sulk: [18] Sulk was a back-formation from sulky [18], which in turn was derived from the now obsolete sulke ‘sluggish’ [17]. It has been plausibly suggested that this may have been descended from Old English āsolcen ‘sluggish, inactive’, an adjectival use of the past participle of āseolcan ‘be lazy or slow’. In the mid-18th century the term sulky was applied to a ‘singleseat carriage’, from the notion of the ‘standoffishness’ of a lone driver.
