Past tense and past participle of begird; encircled or surrounded completely.
From the Old English verb gyrdan via Middle English begirden. The -t ending marks the past tense in some archaic or dialectal conjugations, similar to how 'burnt' coexists with 'burned.'
Many verbs that are now regular (adding -ed) used to be strong verbs with irregular past forms like girt, gurt, and girn. English is gradually 'regularizing' these old verbs, which shows the language actively simplifying itself over centuries.
Complete word intelligence in one call. Free tier — 50 lookups/day.