tassel on a flag, long haired cow, old man
旄 centers on a decorative tassel or tuft, especially one attached to a flag or banner. The meanings 'long haired cow' and 'old man' are rare, possibly extended uses related to hairiness or a specific historical reference, but the core idea is a tassel or tufted ornament.
旄 combines 方 (a flag or banner) with 毛 (hair), suggesting a tassel or tuft attached to a flag. The extended meanings 'long haired cow' and 'old man' are likely derived from the idea of hairiness or a tuft, but the exact historical development is uncertain.
Picture a flag (方) with a hairy tassel (毛) hanging from it: that tassel is the core meaning of 旄. The long-haired cow and old man are like hairy or tufted things, but the flag tassel is the easiest to remember.
For ボウ, imagine a bow (ボウ) tied to the flag's tassel: the bow hangs from the tassel, and 'bow' cues ボウ.