used in place names, (kokuji)
囎 is a rare kokuji (Japan-made kanji) used only in place names. It has no clear standalone meaning beyond its use as a proper noun.
囎 is a kokuji formed by combining 口 (mouth) with 贈 (to send, give). The exact historical motivation is uncertain, but it likely relates to a place name.
A mouth 口 beside 贈, a character associated with giving, suggests a place name where something is given or spoken. Remember it as a special place-name kanji.
For ソ, imagine a small (小, しょう) place named 囎 where people sew (ソ) gifts together. The sound ソ is like the start of 'sew', tying the place to the act of giving.