Due to its phonetic features, Spanish chocho /tʃótʃo/ (slang) 'vulva'1 (with regional variants chocha, chucha) is considered to be of "expressive origin"2 by Spanish linguists. However, to me it's a loanword from Basque txotxo /tʃótʃo/ (B, G) 'penis' (child word), a variant of tutu (B) 'vulva', (L) 'spout (of a jar)', (Bazt, L), ttuttu /cucu/ (Bazt, L) 'feeding bottle'3.
This etymology refers to the labia ('lips' in Latin), and thus I'd link the above words to Germanic *tut- 'to project' (Dutch tuit ‘spout, nozzle’, Middle Dutch tute ‘nipple, pap’, Middle Low German tute ‘horn; funnel’), Kartvelian (Georgian) čˀočˀ- 'peak, tip, spout (of a jug)', East Caucasian *t(t)ʃot(t)ʃV 'tip, spout' (Chechen cˀuzam 'spout (of a tea-pot, jug)', Lezghian cˀucˀ 'spout (of a tea-pot), Kryz cˀɨcˀ 'clitoris; ring-stone'), and Tungusic *tʃitʃu- 'penis, spout (of a tea-pot)'.
1 The homonymous chocho 'white lupin' is a loanword from Mozarabic śóś < Latin salsu- 'salted'. See F. Corriente (2003): Diccionario de arabismos y voces afines en iberorromance, p. 287.
2 It must be remarked that expressiveness (a goal which can be achieved by mimicking children language, as in e.g. expressive palatalization, extensively used in Basque for conveying an affective or diminutive meaning) doesn't necessarily implies a phonosymbolic (i.e. onomatopoeic) origin.
3 There's also the homonymous tutu, ttuttu 'tube, pipe; horn, bugle', conflated by Bengtson.