The name is tenuously related to the trope at best.
Regrowing tails aren't a defining feature of geckos, which range from everything from shooting faeces in the faces of predators, to climbing up walls with cups on their feet, to limited color changing. Many other creatures have similar limb regrowth.
Gecko is not thought of just in terms of the trope, so it's not distinct enough of a term to indicate this trope without reading the description.
The name does not indicate this is an adaptation trope.
It's brought in 1,373 people since February 20th of 2009 (546 days, 2.5 people per day)
It has 153 internal wicks.
Doing a Google search using the parameters (allintext "Gecko ending" -Fallout) returns 1,490 hits of people using the term in the text of a page that is not about the character Gecko's ending in Fallout.
Out of all the usages on the main page at least 50% used it incorrectly.
Reasons not to rename:
Appears to be used outside the wiki in fan communities.