Etymology From Middle English clensen, from Old English clǣnsian, from Proto-West Germanic *klainisōn, from Proto-West Germanic *klainī (“clean”). Cognate with West Frisian klinzgje (“to clean, cleanse”), archaic Dutch kleinzen (“to clean, purify”), Middle Low German klênsen, kleinsen, clensen (“to purify”).
1
To free from dirt; to clean, to purify.
An artificial kidney these days still means a refrigerator-sized dialysis machine. Such devices mimic the way real kidneys cleanse blood and eject impurities and surplus water as urine.2013 June 1, “A better waterworks”, in The Economist, volume 407, number 8838, page 5 (Technology Quarterly):
2
To spiritually purify; to free from guilt or sin; to purge.
[T]he famous Ganges: whoſe vnknowne head, pleaſant ſtreames, and long extent, haue amongſt thoſe Heathen Inhabitants, (by the Tradition of their Forefathers) gained a beliefe of clenſing all ſuch ſinnes, as the bodies of thoſe that waſh therein brought with them: [...]1626, William Methold [i.e., William Methwold], “Relations of the Kingdome of Golchonda, and Other Neighbouring Nations within the Gulfe of Bengala, Arreccan, Pegu, Tennassery, &c. […]”, in [Samuel] Purchas, Purchas His Pilgrimes. […], 5th part, London: […] William Stansby for Henrie Fetherstone, […], →OCLC, book, page 993:
3
To remove (something seen as unpleasant) from a person, place, or thing.
Etymology From Middle English clensen, from Old English clǣnsian, from Proto-West Germanic *klainisōn, from Proto-West Germanic *klainī (“clean”). Cognate with West Frisian klinzgje (“to clean, cleanse”), archaic Dutch kleinzen (“to clean, purify”), Middle Low German klênsen, kleinsen, clensen (“to purify”).
1
An act of cleansing; a purification.
I regularly visit the spa for a massage and a facial cleanse.