solitaire n.

c. 1500, "widow;" 1716, "person who lives in solitude, recluse," from French solitaire, from Latin adjective solitarius "alone, lonely, isolated" (see solitary). The sense of "a precious stone set by itself" is from 1727. The meaning "card game played by one person" (usually involving bringing shuffled cards into sequence) is attested by 1746.

Solitarian "a recluse" is by 1650s; solitary (n.) was in Middle English as "hermit, religious recluse" (late 14c.), "person without companions" (early 15c.). Latin solitarius in Late Latin also was a noun, "anchorite."