From Middle English song, sang, from Old English song, sang (“noise, song, singing, chanting; poetry; a poem to be sung or recited, psalm, lay”), from Proto-Germanic *sangwaz (“singing, song”), from Proto-Indo-European *sengʷʰ- (“to sing”). Cognate with Scots sang, song (“singing, song”), Saterland Frisian Song (“song”), West Frisian sang (“song”), Dutch zang (“song”), Low German sang (“song”), German Sang (“singing, song”), Swedish sång (“song”), Norwegian Bokmål sang (“song”), Norwegian Nynorsk song (“song”), Icelandic söngur (“song”), Ancient Greek ὀμφή (omphḗ, “voice, oracle”). More at sing.
From Old Norse sæing (“bed”), later sæng.
From English song.
From Proto-Tai *soːŋᴬ, from Middle Chinese 雙 ( ʃˠʌŋ, “two”). Cognate with Thai สอง (sɔ̌ɔng), Northern Thai ᩈᩬᨦ, Lao ສອງ (sǭng), Lü ᦉᦸᧂ (ṡoang), Tai Dam ꪎꪮꪉ, Shan သွင် (sǒang), Tai Nüa ᥔᥩᥒᥴ (soang1), Ahom 𑜏𑜨𑜂𑜫 (song).