Hand holding
Hand holding was the act of clasping hands with another. It could be done to show affection, to offer reassurance and guidance, or keep one's child from running off.
Participants in Argelian empathic contact also held hands. In 2267, Montgomery Scott and those participating in Sybo's attempts to discover who murdered women that he was accused of killing held hands. (TOS: "Wolf in the Fold")
In 2366, Lal learned that Humans held hands as a symbol of affection. (TNG: "The Offspring")
In 2372, when their Trill symbionts reunited, Lenara Kahn and Jadzia Dax held hands at dinner, something Doctor Hanor Pren noticed. (DS9: "Rejoined")
In 2375, Julian Bashir and Ezri Dax left Quark's holding hands, something Odo noticed. (DS9: "The Emperor's New Cloak")
Metaphorically, it referred to any act of offered comfort or direction that the recipient of same required in order to be able to perform their duties. (TNG: "Peak Performance"; DS9: "Equilibrium")