sulkyoudaoicibaDictYouDict
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.
single (n.)youdaoicibaDictYouDict
c. 1400, "unmarried person," mid-15c., "a person alone, an individual," from single (adj.). Given various technical meanings from 16c. Sports sense is attested from 1851 (cricket), 1858 (baseball). Of single things from 1640s. Meaning "one-dollar bill" is from 1936. Meaning "phonograph record with one song on each side" is from 1949. Meaning "unmarried swinger" is from 1964; singles bar attested from 1969. An earlier modern word for "unmarried or unattached person" is singleton (1937).