Phonetic transliteration of Western diminutives like 'Gigi', 'Gilly', or 'Jilly' as encountered in subtitle corpora.
吉 ('auspicious') is a common name-syllable choice for the 'gi/ji' sound, also seen in
吉米 (Jimmy) and
吉娜 (Gina);
历 picks up the 'li' sound.