Mattress protector
The mattress protector is the piece that sits between the mattress and the fitted sheet to shield the former from perspiration, stains and wear. Available as an elasticated cover (fitted-sheet style) or a flat pad with corner straps, absorbent (cotton molleton) or waterproofed (with a membrane), it extends a mattress's life by years.
In short-term rental, the protector is not optional: it is what takes the accident and saves the mattress — a stained mattress is unsellable in photos and expensive to replace, while a protector washes at 60°C or is replaced for a few dozen dirhams. Plan two per bed (one on, one spare), just as you do for sheet sets.
And in Arabic?
واقي المرتبة — غطاء يحمي المرتبة من البقع