I think I know where the designations came from:
New ice, nilas and young ice[edit]
Nilas in Baffin Bay
New ice is a general term used for recently frozen sea water that does not yet make up solid ice. It may consist of frazil ice (plates or spicules of ice suspended in water), slush (water saturated snow), or shuga (spongy white ice lumps a few centimeters across). Other terms, such as grease ice and pancake ice, are used for ice crystal accumulations under the action of wind and waves.
Nilas designates a sea ice crust up to 10 centimetres (3.9 in) in thickness. It bends without breaking around waves and swells. Nilas can be further subdivided into dark nilas – up to 5 cm (2.0 in) in thickness and very dark, and light nilas – over 5 cm (2.0 in) in thickness and lighter in color.
Young ice is a transition stage between nilas and first-year ice, and ranges in thickness from 10 cm (3.9 in) to 30 cm (12 in), Young ice can be further subdivided into grey ice – 10 cm (3.9 in) to 15 cm (5.9 in) in thickness, and grey-white ice – 15 cm (5.9 in) to 30 cm (12 in) in thickness. Young ice is not as flexible as nilas, but tends to break under wave action. In a compression regime, it will either raft (at the grey ice stage) or ridge (at the grey-white ice stage).
First-year sea ice[edit]
Distinction between 1st year sea ice (FY), 2nd year (SY), multiyear (MY) and old ice.
First-year sea ice is ice that is thicker than young ice but has no more than one year growth. In other words, it is ice that grows in the fall and winter (after it has gone through the new ice – nilas – young ice stages and grows further) but does not survive the spring and summer months (it melts away). The thickness of this ice typically ranges from 0.3 m (0.98 ft) to 2 m (6.6 ft).[5][6][7] First-year ice may be further divided into thin (30 cm (0.98 ft) to 70 cm (2.3 ft)), medium (70 cm (2.3 ft) to 120 cm (3.9 ft)) and thick (>120 cm (3.9 ft)).[6][7]
Old sea ice[edit]
Old sea ice is sea ice that has survived at least one melting season (i.e. one summer). For this reason, this ice is generally thicker than first-year sea ice. Old ice is commonly divided into two types: second-year ice, which has survived one melting season, and multiyear ice, which has survived more than one. (In some sources,[5] old ice is more than 2-years old.) Multi-year ice is much more common in the Arctic than it is in the Antarctic.[5][8] The reason for this is that sea ice in the south drifts into warmer waters where it melts. In the Arctic, much of the sea ice is land-locked.
https://en.wikipedia.org/wiki/Sea_iceWhich makes perfect sense!