This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
筕 combines 竹 (bamboo) and 行 (go, line). The exact historical development is uncertain, but it likely relates to bamboo mats or woven bamboo items, as suggested by the kun reading たけむしろ (bamboo mat).
Bamboo 竹 arranged in lines 行 suggests a woven bamboo mat. Picture bamboo strips laid out in rows to form a mat.
For コウ, imagine a bamboo mat woven so tightly it can hold a cup of コーヒー (coffee) without spilling: コーヒー -> コウ.