linchpin
definition
a person or thing that holds something together
example
In our team, Sarah is the linchpin who connects all the different departments and ensures everyone is on the same page.
synonyms
keystonelinchanchor
word origin — The term 'linchpin' derives from the Old English 'lyncepin,' where 'lync' means 'to fasten' and 'pin' refers to a small rod or bolt used to keep something in place.