The pseudo-Geber in the 13-14th century (sometimes attributed to Arabic alchemist Jabir ibn Hayyan or Geber from 9th century) in his Summa perfectionis magisterii refers to it as both mercury ( Mercurio) and quicksilver ( argento uiuo). As pointed in the comments, mercury was one of the most important alchemical elements thought to be one of the main ingredients for the philosopher's stone, which allegedly turned normal metals into gold.

You can look at tables of alchemical symbols where elements are always associated with some astronomical body and quicksilver is represented by ☿ (Mercury). Tracking exactly when 'mercury' became more popular than its alternative name quicksilver is hard, as one will have to search for meaning. Mercury-quicksilver, Venus-copper, Mars-iron, Jupiter-tin, Saturn-lead. The first known mention of planet Mercury in association to Hydrargyros is found in a list by Stephanus of Alexandria from the 7th century: Sun-gold, Moon-silver, The association of traditional metals with the planets dates already back to the 2th century CE (in a passage of Celsus preserved by Origenes mercury gets associated with iron).

Mercury was initially known Hydrargyros (in the times of Aristotle) and later known in its liquid state as Argenturn Vivurn translated “alive silver” or in English as “quicksilver' in the 4th century BCE.

Quicksilver metal