The Phoenician letter appears to be named after a sword or other weapon. In Biblical Hebrew, zayin (זין) means "sword", and the verb lezayen (לזיין) means "to arm". In modern Hebrew, zayin (זין) means "penis" and lezayen (לזין) is a vulgar term which generally means to perform sexual intercourse (similar to "fuck"), although the older meaning survives in maavak mezuyan ("armed struggle") (מאבק מזוין) and beton mezuyan (בטון מזוין) ("armed, i.e., reinforced concrete"). The Proto-Sinaitic glyph may have been called ziqq, based on a hieroglyph depicting a "manacle".
It is one of several Hebrew letters that have an additional meaning as a noun. The others are: bet [ב, the 2nd letter], whose name is a grammatical form of the word for 'house' (בית); vav [ו, the 6th letter], whose name means 'hook' (וו); kaf [כ, the 11th], whose name means 'palm [of the hand]' (כף); ʻayin [ע, the 16th], whose name means 'eye' (עין); pe [פ, the 17th], whose name means 'mouth' (פה); qof [ק, the 19th], whose name means 'monkey' (קוף); shin [ש, the 21st], whose name means 'tooth' (שין); tav [ת, the 22nd], whose name means 'mark' (תו), and several other Hebrew letters, whose names are ancient Hebrew forms of nouns still used, with a slight change of form or pronunciation, as nouns in modern Hebrew.
The letter is named zayn/zāy/zāʾ. It has two forms, depending on its position in the word:
Position in word:
The similarity to rāʼ ر is likely a function of the original Syriac forms converging to a single symbol, requiring that one of them be distinguished as a dot; a similar process occurred to jīm and ḥāʼ.