Many aquatic creatures are renowned linguists. Water transmits sound efficiently over massive distances, so chatter builds up and exposure to a huge number of languages is common.
With long lives, a love of gossip, inquisitive personalities, and high levels of intelligence, mermaids are among the most proficient polyglots in the Netherworld.
Mermaids are often hired by sailors and explorers to navigate the sea’s complex and often dangerous barriers in language and culture. This is a risky proposition for rude or combative sailors as the mermaid will always side in favor of the aquatic party in times of conflict (regardless of previous agreement).