Update term set display name via code

Hi All

I have a list, when user creates a new item I am creating new term set by calling below code on PreSave :

function CreateTerm(key, value)
        {   
            try{
            var dfdZ = $.Deferred();
            if (iscreated )
            {
                iscreated = false;
                var context = SP.ClientContext.get_current();

                //defines current Taxonomy Session
                var taxSession = SP.Taxonomy.TaxonomySession.getTaxonomySession(context);

                //Term Stores
                var termStores = taxSession.get_termStores();

                //get the Termstore by Termstore name
                var termStore = termStores.getByName("Taxonomy_bJik8sNfJ/Yz3Z2wP+SPHg==");

                    var guid= key;
                    var termname = value;
                    var termSet = termStore.getTermSet(guid);
                    var newguide =CreateGuid() ;
                    var newTerm = termSet.createTerm(  termname, 1033, newguide);

                    context.load(newTerm);
                    context.executeQueryAsync(function () {
                    iscreated = true;
                    dfdZ.resolve(iscreated);

                }, function (sender, args) {
                    console.log(value + " termname already exist " +  args.get_message());
                    iscreated = true;
                    dfdZ.resolve(iscreated);
                });
                return dfdZ.promise();
            }
            else
                {
                    setTimeout(function(){
                        CreateTerm(key, value)
                        }, 2000);
                }
            }
            catch(error)
            {
                console.log('Error: '+error);
            }
        }

    function CreateGuid() {  
        function _p8(s) {  
            var p = (Math.random().toString(16)+"000000000").substr(2,8);  
            return s ? "-" + p.substr(0,4) + "-" + p.substr(4,4) : p ;  
        }  
        return _p8() + _p8(true) + _p8(true) + _p8();  
    }

And when user edits the item, I need to edit the display name of term set dynamically. I am unable to figure out how this can be done.

Please help.

Thanks in Advance, Jiniv Thakkar