PLUR

It is derived to us from the Saxon's who declined smith, a smith; Gen. smither, of a smith; Plur.

In declension he never uses -ae as the genitive, but -ai or -as; the older and shorter form of the gen. plur.

When declined like adjectives they drop their e where practicable:—fylled, plur.

Skeat has a note on this word explaining renk as a rank of fighting men, and citing the plur.