This tool uses the CMU Pronouncing Dictionary (filtered down to common English words) to find candidates for spoonerism.
Each word is split into its onset (consonants before the first vowel) and tail (the rest).
For example, "stone" → onset ST, tail OWN.
Words that share a tail are rhymes. When you pick two rhyming words with different onsets (e.g. "stone" and "grown"), we search for other rhyming pairs that have those same two onsets.
This gives us word pairs where swapping the onsets creates valid words - spoonerisms