罵倒する batōsuru scold; revile
罵倒メール batōmēru flame email
罵る nonoshiru to curse at
罒 /网 is net. 馬 is horse and lends its sound ba. Some claim that the original meaning of 罵 was cover with a net, with cover with dirty words as a derivation.¹ However, 詈 ri, also to scold, similarly uses net 罒 /网 as signific, which suggests that 罒 /网 had a specific connotation related to scolding.²
Mnemonic: Scold at the horse that escapes the net
1. Cited on ja.wiktionary.org, no source given. 「网」と音符「馬」を合わせた字で、「网をかぶせる」が原義。そこから派生して、网をかぶせるように「汚い言葉を浴びせる」「ののしる」という意味になった。 (accessed 2016 11 11).
2. The oldest known meaning of 罵 is simply ‘to scold’ (Schuessler). Guessing at an older meaning based on the elements that were used is certainly possible, but in this instance the existance of 詈 constrains speculation.