Another entry on barm in OED. This time as a verb- and "Obs. or arch." 1. To mix with yeast; to leaven, ferment. 1616 SURFL. & MARKH. Countr. Farm 589 Your best ale must be barmed as soone as it is coold. 2. To rise in froth or fermentation. c1440 Promp. Parv. 32/2 Bermyn, or spurgyn as ale, spumo. Johnnae