The speaker tells a funny story about Amos Obadaiah, a neighbour or acquaintance who is grumpy, gruff and proud of it. Amos claims he is really a dragon, and the poem proves him right when a handsome hero turns up and insults him. Amos doesn't fight in any grand way. He calmly burns off the hero's pants, then his sweater, and sends him running away, embarrassed and unclothed.
The speaker is a mix of amused, admiring and nervous. At the start they admit Amos is "a sort of friend" but wouldn't say so aloud. At the end they cheer, then shrink back under his glare, and still end up sweeping ashes. The mood is playful and light, helped by bouncy rhythm, rhyme and invented words like "gleamsome" and "fierce-ish." Dragon danger turns into comic mischief, and the hero's pride is the real thing that gets burned.