δαιμόνιον daimonion (G1140) is defined in Thayer's Greek Lexicon (published in 1841 by Joseph Thayer) as 1) the divine power, deity, divinity; 2) a spirit, a being inferior to God, superior to men; or 3) evil spirits or the messengers and ministers of the devil. Thayer goes on to state that, "according to a Jewish opinion which passed over to the Christians, the demons are the gods of the Gentiles and the authors of idolatry... Josephus, also makes mention of δαιμόνια daimonion taking possession of men, Antiquities 6, 11, 2f; 6, 8, 2; 8, 2, 5; but he sees in them, not as the N. T. writers do, bad angels, but the spirits of wicked men deceased." There is, however, no reference in the Bible to followers of Yeshua referring to demons as "bad angels."
δαιμόνιον daimonion is equivalent to שֵׁד shed (H7700) which literally means "the two that dangle" in reference to breasts (שַׁד shad H7699 cf. Genesis 49:25; Job 3:12; Psalms 22:9). When related to demons, שֵׁד shed is most often referenced as a goat-demon due to the teats, or breasts, of the goat (cf. Deuteronomy 32:17; Psalms 106:37). In Leviticus 17:7, many translations read, "sacrifices to demons" or "sacrifices to the goat idols." However, the Hebrew is יִזְבְּחוּ לַשְּׂעִירִם yizbechu lase'irim means, "their sacrifices to the hairy goats" where hairy goats is the same term used for the two hairy goats of Leviticus 16:5-8, "...one lot is for YHWH and one lot is for Azazel..." לַשְּׂעִירִם lase'irim literally means "to the hairy goats" where the לַ la is a prefix meaning "to" and שְּׂעִירִם se'irim is the plural of se'ir (H8163) which means hairy goat. The phrase לַשְּׂעִירִם lase'irim "to the hairy goats" is only used once in the Hebrew Bible in Leviticus 17:7 and is often translated as "...sacrifice to demons..." Se'ir (H8165) is the country of Edom (cf. Genesis 32:3), the land possession of Esau (cf. Deuteronomy 2:5), and enemies of Israel (cf. Numbers 24:18).
Interestingly, אֵל שַׁדַּי El Shaddai (H410 + H7706) literally means "Mighty Breasted One" where שַׁדַּי shaddai is derived from שָׁדַיִם shadayim (H7699 & H7700) which means "breasts” (cf. Genesis 49:25) and figuratively represents "abundant provision,” thus El Shaddai can be translated as "God of abundant provision.” The Old Akkadian word for breast was shadwi. The hypothetical derivation of Hebrew shaddai from Akkadian shaddu’a "mountaineer” or shaddu "mountain” is based on phonetic association rather than philology. The Greek Septuagint and Latin Vulgate translated shaddai as "all powerful”.
The Greek Old Testament uses δαιμόνιον daimonion (G1140) in Psalms 91:6, Psalms 96:5, Isaiah 13:21, Isaiah 34:14, Isaiah 65:3, and Isaiah 65:11.

night-demon