remedial (adj.)

1650s, "curing, relieving, affording a remedy," from Late Latin remedialis "healing, curing," from Latin remedium "a cure, remedy, medicine, antidote, that which restores health," from re-, intensive prefix (or perhaps literally, "again;" see re-), + mederi "to heal" (from PIE root *med- "take appropriate measures"). Educational sense of "concerned with improving skills" is by 1879.