Meaning and source of names of maidservants

What is a meaning and source of names of maidservants Devorah, Bilhah, and Zilpah?

Also, what is etymology of the name Hagar, mother of Ishmael?

Devorah:

Devorah (דבורה) means 'bee'. According to Rabbi Ahron Marcus, Barzilai (ברזילי), pp. 75-76, the word comes from the root DBR (דבר), which both refers to speaking, a reference to the bee's buzzing, and to a 'Dabar' (דבר), a person who leads a group and serves as their representative (much like the queen bee leads the hive).

Zilpah:

The meaning of Zilpah (זלפה) isn't entirely certain. According to Encyclopedia Mikrait, vol. II, col. 929, s.v. זלפה, some have suggested it stems from the Arabic 'Zulphah', which refers to a rank of honor. Others have suggested Arabic 'Z'ulif', which means 'be small', or (especially) 'have a small nose'. Per the latter option, perhaps the name indicates diminutiveness. Rabbi Marcus (mentioned above), p. 161 thought the name was Hebraic in origin but did not clarify its meaning.

Bilhah:

The meaning of Bilhah (בלהה) isn't entirely clear. According to Encyclopedia Mikrait, vol. II, col. 132, s.v. בלהה, some have suggested that it stems from the Arabic root 'VaLaHa', which means 'naive' or 'small-minded'. Others have suggested it may be a theophoric name connected to the word balahot (בלהות) from Iyov 30:15. A third possibility is that it's connected to the Horite name Bilhan, and therefore both are of Horite origins (though their meaning is unclear). Rabbi Marcus (mentioned above), p. 161 thought the name was Hebraic in origin but did not clarify its meaning.

Hagar:

The meaning of Hagar (הגר) isn't entirely clear. According to Encyclopedia Mikrait, vol. II, col. 784, s.v. הגר, parallel names are known from various ancient Arabian languages such as Sabean and Minean, but the true meaning remains elusive. Southern Arabian dialects have a similar word, HGR, which means 'city' or 'district'. Wikitionary suggests comparing to the Hebrew root גור, which means 'stranger' (as in 'ger', גר) and the Classic (Late Antiquity-early Medieval) Arabic 'Hajar' (هَاجَر) which means 'to migrate', 'to separate from one's own', 'to abandon the nomadic life' (and from here the Hijra). Whether these have any connections to Hagar's name remains unknown (keeping in mind that she was Egyptian in origin).