mid-14c., bede "prayer bead," from Old English gebed "prayer," with intensive or collective prefix *ge- + Proto-Germanic *bidjan "to pray, entreat" (cf. Middle Dutch bede, Old High German beta, German bitte, Gothic bida "prayer, request"), from PIE *gwhedh- "to ask, pray." Shift in meaning came via beads threaded on a string to count prayers, and in phrases like to bid one's beads, to count one's beads. German cognate Bitte is the usual word for conversational request "please." Also related to bid (Old English biddan) and Gothic bidjan "to ask, pray." Sense transferred to "drop of liquid" 1590s; to "small knob forming front sight of a gun" 1831 (Kentucky slang); hence draw a bead on "take aim at," 1841, U.S. colloquial.
1570s, "to adorn with beads," from bead (n.). Meaning "to string like beads" is from 1883. Related: Beaded; beading.
To take very careful aim at something or someone; concentrate successfully; zero in: She has, however, got a bead on her five original characters
[1841+; fr the beadlike appearance of the front sight of a rifle; the date is for the draw form]