Right-hand means on or towards the side opposite the heart. The right-hand lane.
The hyphenated form is the one that pairs with side, corner or lane. A right-hand man is the person somebody relies on most, from the same idea of the stronger hand.
1adjectiveright-handOn or towards the side opposite the heart, in the hyphenated form that pairs with side, corner, or lane.
“The switch is in the right-hand corner behind the door.”
right-hand is a quality.
Old English rihthand, right plus hand. About nine people in ten are right-handed, which is why so many tools and turnstiles assume it without saying so.
Old English
rihthand — right-hand
Middle English
ryghte-hande
English, today
right-hand
From Middle English ryghte-hande, from Old English rihthand (“right-hand”), equivalent to right + hand.
Etymology from Wiktionary, CC BY-SA