The item configuration page located in Configuration->Hosts::Items contains 'Clear history' button that actually clears history and trends from a database and works similarly to the 'Clear history and trends' button located in the Item configuration form. e.g.

Steps to reproduce:

• Create host with numeric item (default history and trends storage period)
• Run the server and collect data for the item so there will be entries in history_uint and trends_uint table
• Go to Configuration->Hosts::Items and find your created item (filter by Hosts)
• Select the item and press 'Clear history' button
• Check the item history_uint and trends_uint entries in database.

Result: History and trends are cleared (No entries in database for a particular item).

I suggest using one name for both buttons and renaming the button 'Clear history' to 'Clear history and trends'.

Note: maybe this can be done in terms of ZBXNEXT.