Lyudiye stands thirteenth, writes l, and carries the numeral 30 from Greek lambda. Its name is the Slavonic plural noun for people, a word that in the liturgy usually means the congregation, the people standing in the church as against the clergy serving in it.
The shape is the uncial lambda, drawn as a pointed arch, and the modern printed form descends from it directly. In the older hands the left stroke often carries a foot and the right does not, which is one of the small asymmetries that distinguish an early Cyrillic page from a Greek one.
As a numeral it is 30, and it is one of the letters a reader of liturgical books meets constantly, because the psalter, the calendar and the eight tone cycle all generate numbers in the thirties.
The word it is named for is worth a moment. Almost every letter name in the set is a word from the shared vocabulary of worship: I, know, word, good, it is, people, ours, rest, say. Set out in order they read less like a list of sounds than like the furniture of a liturgy, and that is not an accident. The alphabet was taught from the books it existed to carry, and a child learning the letters was learning, at the same time, the words those books were made of.