First, make sure that SecondLife /isn't/ running while you do this.
Next, find panel_toolbar.xml (On my computer it's C:\Program Files\SecondLife\app_settings\panel_tool
Open it in Notepad.
Find the part that reads:
name="directory_btn"
label="Search"
tooltip="Search for places, events, people, and more."
and change it to read as:
name="directory_btn"
label="Find"
tooltip="Search for places, events, people, and more."
Save the file, you're done. :D