From coutumier + -ment. <span class="searchmatch">coutumièrement</span> customarily; usually; habitually “<span class="searchmatch">coutumièrement</span>”, in Trésor de la langue française informatisé [Digitized Treasury...
coustumiere + -ment. coustumierement usually; normally; as a norm French: <span class="searchmatch">coutumièrement</span>...