言葉を濁す (kotoba o nigosu: to be elusive, to make things less lucid on purpose, not to commit to something) word + to muddy
The last character here, 濁, also appears in 濁り (nigori), which means “voicing.” In addition to meaning “to muddy,” 濁 means “uncleanness; wrong; impurity.” A voiced sound is considered “impure.” Take, for example, an expression we’ve just seen:
言葉尻を捉える (kotobajiri o toraeru: to cavil at a person’s words) word + buttocks + to capture
The jiri in kotobajiri is voiced. The “pure,” “clear,” or “unmuddied” version is shiri. If you want to know how to purify buttocks, there you go!