The below is based around archers in English armies in the 14th and 15th century:

The closest to a 'direct translation' would most likely be along the lines of "Nock... Draw.. Loose." However, it's highly unlikely this was ever used in a similar fashion to commands used by line infantry during the period you mention.

One key thing to bear in mind is that the "Draw...Loose" part of this command is difficult as drawing a bowstring back can be very physically demanding. Bows used for war could often have a draw weight of roughly 100-160lbs (45-72kgs) and so holding this amount of weight whilst waiting for the command to shoot would be exhausting.

Once bows were drawn they would tend to be loosed almost straight away. This is partly due to physical limitations mentioned above and also because with bows, rate of fire is key. A good archer could be expected to loose an arrow roughly every 5-7 seconds and so there isn't really time for specific 'volley' commands. However, there would be commands instructing archers when to commence loosing arrows and when to cease.

Finally, whilst medieval armies were (especially in the later periods) largely made up of professional soldiers, discipline and order was based more on the army's overall conduct (related to looting or to uncoordinated attacks/retreats) rather than drilling specific tactics such as volley fire:

"English military ordinances concentrated on the organisation and discipline of the forces, and assumed all those present were competent soldiers... and so included little provision for drill and tactical practice" - R. Wadge.

Sources used for my answer were mostly from 'The Longbow' by Mike Loades and 'Arrowstorm' by Richard Wadge.
Some great detail on how archers could be deployed and organised in battle is included in '24 hours at Agincourt' by Michael Jones too.