An Etymological Dictionary of the German Language/brennen
brennen, vb., ‘to burn, scorch, sting, distill’; it combines the meanings of MidHG. brinnen, str. vb., ‘to burn, give light, shine, glow,’ and its factitive brennen, wk. vb. ‘to set fire to, cause to burn’; the former is Goth., OHG. and OLG. brinnan, ‘to burn’ (intrans.), the latter Goth. brannjan, ‘to set fire to.’ Comp. AS. birnan (intrans.), bœrnan, bernan (trans.). E. to burn, is trans. and intrans., like the ModHG. word. Under Brand attention is called to the fact that only one n of the Goth. verb. brinnan belongs to the root; the second n is a suffix of the present tense (comp. also rinnen, rennen); the form with simple n is seen in AS. bryne, ‘conflagration’ (from bruni). A root bren-, pre-Teut. bhren, with the meaning ‘to burn,’ has not yet been authenticated in the other Aryan languages.