原句是「腳踏馬屎憑官勢」， 古時候官乘馬，隨從跟後，踩着官員馬匹的遺糞，卻依仗官威欺壓百姓。

take advantage of one's or sb. else's power to bully people; bully others on the strength of one's powerful connections or position; draw one's weight about; have powerful backing and bully the common people