You only need the first 4 letters of BIP39 words

A neat BIP39 detail: each English word is uniquely identified by its first 4 letters.

You can verify it yourself:

for n in 3 4 5; do \
  printf "$n chars: "; \
  curl -fsSL \
    https://raw.githubusercontent.com/bitcoin/bips/master/bip-0039/english.txt \
| cut -c1-$n | sort -u | wc -l; done

Output:

3 chars: 1096
4 chars: 2048
5 chars: 2048

Since the list contains 2,048 words, four characters produce 2,048 unique prefixes. Three aren’t enough, but four are.

https://stacker.news/items/1537637