So Romeo would, were he not Romeo call'd, Retain that dear perfection which he owes Without that title:--Romeo, doff thy name;
Take all myself.
call’dはcalledの省略形。were he not Romeo call'dは仮定法ですね。If he were not called Romeoと同じです。文法的にはwere he not called Romeoなのでしょうが、詩などではリズムを重視して単語の順番を入れ替えることがよくあります。