WHOLE CHARACTER
信xìn, shēn
honest; trustworthy (信用,信守); to believe; to trust (信任,信心); a letter (信件,写信); news; information (信息,音信)
信 is trust and letters: 信心 'confidence', 信任 'trust', 信息 'information', 信封 'envelope'.
ZDIC: 会意,从亻、从言 — a person standing by their word: trustworthy; later a letter.
THE PERSON SIDE (ZDIC 从亻)
亻rén
person (from 人)
Left-side person form; not a standalone page.
In 信: the person side (ZDIC 从亻) The standing-person radical.
THE WORD/SPEECH PIECE (ZDIC 从言)
言yán
speech; words
Speech-related clue in 警.
In 信: the word/speech piece (ZDIC 从言) Shown with its documented or clearly limited role.