sunyoudaoicibaDictYouDict[sun 词源字典]
sun: [OE] Not surprisingly, considering the central importance of the sun to human life, the word for it in the vast majority of modern European languages goes back to a common Indo-European source – *sāu- or *su-. These variants have however differentiated into several distinct camps. The *sāu- form adopted an -lsuffix, and evolved into Greek hélios (source of English heliotrope), Latin sōl (whence French soleil, Italian sole, and Spanish sol, not to mention English solar, solarium, etc), Welsh haul, and Swedish and Danish sol.

The *suform with an -l- ending has given Russian solnce, Czech slunce, Serbo-Croat sunce, etc. But the modern West Germanic languages have inherited the *su- form with an -n- suffix, giving German sonne, Dutch zon, and English sun.
=> heliotrope, solar, solarium[sun etymology, sun origin, 英语词源]
sun (n.)youdaoicibaDictYouDict
Old English sunne "sun," from Proto-Germanic *sunnon (cognates: Old Norse, Old Saxon, Old High German sunna, Middle Dutch sonne, Dutch zon, German Sonne, Gothic sunno "the sun"), from PIE *s(u)wen- (cognates: Avestan xueng "sun," Old Irish fur-sunnud "lighting up"), alternative form of root *saewel- "to shine; sun" (see Sol).

Old English sunne was feminine (as generally in Germanic), and the fem. pronoun was used in English until 16c.; since then masc. has prevailed. The empire on which the sun never sets (1630) originally was the Spanish, later the British. To have one's place in the sun (1680s) is from Pascal's "Pensées"; the German imperial foreign policy sense (1897) is from a speech by von Bülow.
sun (v.)youdaoicibaDictYouDict
1510s, "to set something in the sun," from sun (n.). Intransitive meaning "expose oneself to the sun" is recorded from c. 1600. Sun-bathing is attested from c. 1600.