Alkanna

الكَحْلاء

Alkanna tinctoria

The root of al-kaḥlāʾ, called shinjār in Arabic medical books and al-ḥinnāʾiyya today, holds a dye «red as blood, that stains the hand when touched», so Europeans named it after Arabic al-ḥinnāʾ, henna, article and all: alcanna, then French orcanette and English alkanet; but Arab henna is a leaf you grind, not a root.

Source of the name: From an Arabic word
From the Arabic word: al-ḥinnāʾ, a different plant
Genus: Alkanna
Species shown: Alkanna tinctoria

«الشِّنْجارُ، بالكسر: مُعَرَّبُ شِنْكار، وهو خَسُّ الحِمارِ، ويُسَمَّى الكَحْلاءَ، والحُمَيْراءَ، ورِجْلَ الحَمَامَةِ، وهو نباتٌ لاصِقٌ بالأرضِ مُشَوِّكٌ، له أصلٌ في غِلَظِ إصْبَعٍ، أحْمَرُ كالدَّمِ، يَصْبُغُ اليَدَ إذا مُسَّ.»
al-Fayruzabadi (d. 1415), al-Qamus al-Muhit, p. 420

The path between languagesal-ḥinnāʾ → alcanna → Alkanna

More on this word

Modern Arabic calls it al-ḥinnāʾiyya, after the very name botanists gave it (Arabic Wikipedia). Its best-known name in Arabic books is shinjār; Ibn Sina's Canon calls it «donkey's lettuce» whose stem «turns blood-red in summer, so that it stains the hand». Al-Qamus adds al-kaḥlāʾ, al-ḥumayrāʾ and «dove's foot»; colloquially it was also «ghoul's henna» (Dozy, Supplément).

Wadghiri (2/233): orcanette comes from Old French alcanne/alchane, 'taken directly from Arabic al-ḥinnāʾ, or through medieval scientific Latin alchanna', and entered English in 1548. It is a Mediterranean plant with dark red roots that yield a dye.

He adds (2/234) that the henna of the Arabs and of Arabic botany is a leaf ground to give the red henna colour, not a root: 'perhaps these roots were something else, likened to henna for the colour'.