Student refused UK visitor visa [duplicate]

I am a Vietnamese national, who is studying in Nicosia, Cyprus since June 2016, in a four-year Bachelor's degree program in business administration. My application for UK tourist visa was submitted on 13 December 2016 and was refused on 20 December 2016.

Submitted document list:

• Student residence permit (valid until 05 June 2017)
• College registration letter
• College holiday letter
• Student card
• Six months bank statements (including 3 receipts of money transfers from mother in Vietnam)
• House contract (for 2 years until June 2018)
• Air ticket reservation
• Hotel reservation
• Travel insurance

Included mother's documents as follows:

• Business license
• Tax for the last three month
• Annual tax
• Sponsor letter
• Property in mother's name
• Bank letter with balance equal to 12,000 Pounds (which issued from 01/03/2016-01/03/2017)
• My birth certificate

The decision: You have applied for an entry clearance as a General Visitor to the United Kingdom for 6 days and propose tourism.

You have declared that you are a student and not employed. Whilst you have included customer credit transfers these do not evidence the original source of the funds, I am therefore not satisfied that your circumstances are such that you would leave the UK if admitted.

You state that you spend between 600-650 pounds per month on living costs, you have not demonstrated how you support yourself and the source of the funds. You state that you will have 2500 pounds available for your trip. Given your financial circumstances, balanced against your proposed expenditure I am not satisfied that you would leave the UK if admitted.

The financial documents you have submitted do not show the origin of the funds and therefore I am not satisfied that they are genuinely available to you. From the information declared on your application form and the documents submitted, you have not shown that you will be able to maintain and accommodate yourself during your proposed visit in the UK your application has therefore been refused under paragraph V4.2（e)

The customer credit receipts reflected on my bank statement are transfers from my mother for living expenses. Why was the ECO confused about where the funds originate? What should I do in the next application？