What ㌷ means
It packs the Japanese katakana spelling ペソ into one cell. Japanese typesetting used boxed katakana words to fit short forms into an ideographic cell in dense text. In vertical Japanese text, the components can be arranged differently than in horizontal lines.
Japanese records attest to the spelling ペソ from 1860; that dates the word, not this boxed form. Squared-word characters passed from older Japanese character encodings into Unicode. NFKC and NFKD are compatibility-normalization forms: text processing that applies them expands this one-cell form to the ordinary sequence ペソ.
Don't confuse it with
2Questions people ask
1Why does ㌷ show as a box on some devices?
Because that device's fonts have no glyph for it. The character is still correct and still copies correctly — the box is a missing glyph, not a broken character.
How to type ㌷
㌷\3337Codes and encoding1 code points
A visible symbol can contain several code points. JS .length counts UTF-16 units; UTF-8 counts bytes.