You could change Strings.STS.L_EditItem_Text, its where the ECB gets its value for "Edit Item". It could be used different place, so probably best to change it only when the CallOut on the ECB is used.

A possible solution could look like this, I dont have much experience with the OOTB ECB tbh, so there could be some better options out there.

$(".ms-list-itemLink").each(function(e,i)  { 
    
    $(this).click(function() {
        
        CalloutManager.forEach(function(i) {
            var stsValue = Strings.STS.L_EditItem_Text;
            if(i.isOpening) {   

                i.addEventCallback("closing", function() { 
                    Strings.STS.L_EditItem_Text = stsValue;
                });
                
                i.addEventCallback("opening", function() { 
                    Strings.STS.L_EditItem_Text = "Something else";
                });
    
            }
        });
        
        Strings.STS.L_EditItem_Text = "Something else";
        $(this).unbind("click");
    });
});  

You could change Strings.STS.L_EditItem_Text, its where the ECB gets its value for "Edit Item". It could be used in different places, so probably best to change it only when the CallOut on the ECB is used.

A possible solution could look like this, I dont have much experience with the OOTB ECB tbh, so there could be some better options out there.

$(".ms-list-itemLink").each(function(e,i)  { 
    
    $(this).click(function() {
        
        CalloutManager.forEach(function(i) {
            var stsValue = Strings.STS.L_EditItem_Text;
            if(i.isOpening()) { 

                i.addEventCallback("closing", function() { 
                    Strings.STS.L_EditItem_Text = stsValue;
                });
                
                i.addEventCallback("opening", function() { 
                    Strings.STS.L_EditItem_Text = "Something else";
                });
    
            }
        });
        
        Strings.STS.L_EditItem_Text = "Something else";
        $(this).unbind("click");
    });
});